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Given the sun as the source of light for the above question, does the incident of different visible wavelengths same on a given surface, at a particular time and duration, even if the sun is rotating at a constant speed.

user10867746
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  • Light from the sun is not pure white light, but rather a spectrum based on the elements of the sun's composition. Analyzing the sun's spectral lines, you'll notice specific bands missing at particular wavelengths, which should be 'constant' if unobstructed.. until certain processes cause changes in the sun which affect the wavelength of light it is emitting. – bleuofblue Mar 05 '22 at 23:25
  • Why should the rotation of the Sun (about 27 day period of rotation) have anything to do with the spectrum of light the sun emits? – Dan Mar 06 '22 at 00:56
  • @blueofblue so Sun light won’t result in continuous spectrum in prism? which source gives pure white light. – user10867746 Mar 06 '22 at 01:52
  • @Dan Rotation of sun is ~1.2 miles per second. Is the distribution of wavelengths same on a given surface at a given time? – user10867746 Mar 06 '22 at 01:57
  • https://www.nrel.gov/grid/solar-resource/spectra-am1.5.html – Anonymous Physicist Mar 06 '22 at 02:05
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    "White" is not uniquely defined. – Anonymous Physicist Mar 06 '22 at 02:06
  • @AnonymousPhysicist So an unobstructed light from a source falling on a surface does all those incident rays have same wavelength at a given time or each incident wavelength on a given surface is random at a given point? If this is the case the image we see should change its pixel every time it is clicked over very short time. – user10867746 Mar 06 '22 at 02:15
  • May be my answer here will help https://physics.stackexchange.com/questions/605951/what-actually-is-white-light/605969#605969 . There is perception of color by humans, and the spectral colors. https://en.wikipedia.org/wiki/Color_vision – anna v Mar 06 '22 at 06:56

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A ray is a geometrical definition of the direction of classical light waves:

In optics a ray is an idealized geometrical model of light, obtained by choosing a curve that is perpendicular to the wavefronts of the actual light, and that points in the direction of energy flow.

Thus the content in frequencies/wavelengths of a ray is the same as the content in the mathematical description of electromagnetic waves.

The colors of the spectrum are not one to one with the colors our eyes have defined. The spectrum from a crystal have specific frequencies that we have named with the color we see, and there, there is a one to one correspondence, frequency to color. Note there is no "white" in the spectrum:

visible spectrum

But our eyes can see the same named colors with a combination of light frequencies, called color perception:

colorperc

The color perceived at point T , comes from a combination of frequencies, and many different pairs give the same perceived color. White in this plot is around the achromatic point. Please read the link for details.

In summary, white is not a color in the visible light spectrum, many frequencies could make up the perception of white color, which means that photons of a large variation in energies make up the white color.

At the quantum level, light is a confluence of zillions of photons that combine to give the classical electromagnetic wave, for references see this.

The figure shows how the frequencies combine to give the perception of white. One needs many photons for our eyes to be able to perceive them, but even a few hundreds can give a signal to the brain, this link might interest you.

The answer your "What is the distribution of different wavelengths in single ray of white light?" is:

The distribution is not unique to give the perception of white light. There are very many frequencies/wavelengths as seen in the plot that will give "white". It will depend on the production mechanism.

If the light front started as white from the sun, and if it does not interact with any particles or fields on the way, the phases between the different frequencies/waves will be fixed, so it will arrive with the perception of white light with the same frequency/wavelength distribution it started with, still giving the perception of white. .

anna v
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